Further to my comment on 18 June, management of ocean currents has strong potential to slow Arctic warming.

Reducing heat entering the Arctic Ocean could well be the most effective way to slow global warming, while preparing for transition to a low carbon economy.

The Arctic is warming at double the rate of the rest of the planet. This appears to be largely due to albedo - the melting of summer sea ice means that instead of white ice reflecting light back to space, dark water allows light to enter, where it turns into heat, producing a feedback loop of increasing pace of summer ice melt. The Arctic is also particularly significant for the global climate because of the potential for methane release from melting permafrost, and because the midnight sun means that level of solar light is high in summer. If entering heat can be reflected rather than absorbed the Arctic is possibly the most efficient and ecologically beneficial location for geoengineering.

As well as sunlight, the major source of heat entering the Arctic is the Gulf Stream, the Atlantic Current that warms Britain and Norway, entering the Arctic via the Norwegian Sea.

If a large fraction of the heat in these north flowing currents could be siphoned off and shifted either into energy production or sunk into the cold south flowing currents, it would provide a significant contribution to slowing the melt of summer Arctic Ice, and to increasing Arctic albedo.

One way to achieve this diversion of heat entering the Arctic is locating large reflecting sheets of plastic just below the ocean surface to trap and reflect the entering solar heat in the surface layer of water. Trapped heat could be used for algae and fish production, or alternatively, could be pumped using wave power down into cold deep currents where it would flow south away from the Arctic. On industrial scale this method would have material impact on planetary climate.

There is global warming which could be attributed to weakening of the magnetic field by 10% over the last 150 years and by only 5% over the last 30 years. There is always climate ex-change. While the ice cap is melting in the Arctic, the ice sheet is growing in the Antarctic. Temperature belts are very much influenced by the location of the magnetic pole as well as the strength of the magnetic field. The south magnetic pole in the Arctic is moving from Canada towards Siberia. The temperature belts are accordingly tilting. This explains why North America is getting warmer while northern Siberia is getting colder. Global Warming and Climate Ex-change is not anthropogenic. There is a cycle and sound history and geology records speak of it. The challenge would be to design and effect the right strategies to transform basic industries such as Agriculture, Energy, Infrastructure, ..to a new paradigm.

You're "The Economist", not "The Scientist" (which, I guess, is good, since this is junk Science).
How does this winter's Bering Sea ice event (which affected Economics much more suddenly, and drastically than anything you discuss) fit in with your hypothesis?
Stop shilling for the warmists. They are just looking for ways to gain power and coin.
A one-world cap and trade, or taxation, regimen is simply unworkable, even IF the Anthropogenic CO2 warming hypothesis were true.
Do you SERIOUSLY believe that the $ paid to governments would be used to reduce emissions? Even more laughable, are you seriously trusting that the tropical kleptocracies and corrupt regimes of Latin America and Africa will actually use the transfer payments in the ways intended, or report accurately on the results?
Central planning doesn't work.
Example A: Communism
Example B: The slow train wreck that is the EU.

Are the Royal Society fellows being scientists or communists when they say "It is certain that increased greenhouse gas emissions from the burning of fossil fuels and from land use change lead to a warming of climate, and it is very likely that these green house gases are the dominant cause of the global warming that has been taking place over the last 50 years".

What pains me most is the appaling economic consequences of not tackling anthropogenic global warming. You somehow think that the damage businesses such as mine may suffer from an economy strained by the need to deal with rising temperatures, sea levels and weather extremes can be ignored. Why? Communists ruined economies. Why do you wish to join them?

More scare tactics to push Globalism and funding . Let it melt who cares ? We are on the verge of WW3 and your worried about a little ice melting ? The only global warming you should worry about is from a all out nuclear exchange . Worried about a few sandbars they call countries ?

I am totally baffled by the way half of you people are going out of your way to look for reasons to argue that climate change is either not happening or not man-made. It is almost beyond doubt that it is happening and we caused it.
But let's just say that it is not certain, but just likely. Even then, we would be crazy not to respond through energy efficiency measures and alternative energy sources. What's the worst that could happen if climate change is not, after all, man made? We reduce air pollution, extend the window of finite fossil fuels, discover cleaner energy sources, generate employment....
And regarding these absurd theories that it is some kind of conspiracy to make money - GET A GRIP!! Who is really going to make money out of responses to climate change!? The only ones likely to do so (renewable energy companies) have nowhere near the lobbying power of the oil companies, which are most profitable companies in the world, and the most interested in maintaining the status quo.
And I can guarantee that the scientists working on the subject are not making anything like the kind of money that those who are lobbying against responding to climate change are (e.g. Koch Industries). If there is any "conspiracy" at all, it is the methodical undermining of the climate change consensus by industry-funded lobbying groups that used to work for the tobacco industry. At least these fake "grassroots" campaigns have actually been indisputably exposed, unlike these vague claims about "globalism" and "funding".
This subject is too important to our children and grandchildren to be squabbling over a few percentage points of certainty.
PRECAUTIONARY PRINCIPLE, guys!

The Precautionary Principle is a FALLACY!
If you don't do anything that might have bad consequences, or for which all of the consequences are not understood, you will do nothing.
If humanity had followed the precautionary principle, we would have died out in some cave, because venturing outside was too uncertain.

I think your understanding of risk is different from what HLEBR means by precautionary principle.

Your doctor says your arteries clogging and recommends you diet and exercise. Not liking what you hear, you get a second (and third and fourth) opinion. In fact, the scientific consensus says your arteries are clogging. Precautionary principle: diet & exercise. Who knows, you may never have a heart attack.

Everything carries some risk. What HLEBR argues is the risk of climate change warrants actions to mitigate and manage that risk.

What you describe is not the precautionary principle. The precautionary principle is exactly as I described: it is better to take no action than take an action that might have disastrous consequences. http://en.wikipedia.org/wiki/Precautionary_principle
The GWM crowd are insisting that the corrolary is ALSO true: if taking no action can be shown to have disastrous consequences, then almost any action is better than none.
Both are complete logical fallacies.
Your metaphor is not a valid analogy for the Anthropogenic Global Warming Hypothesis and the mooted fixes to it.
A better analogy would be:
You are gaining weight. You know that if you gain too much weight, there's an increased risk of heart attack. Tie died hippies keep stopping you in the street and screaming at you that you are a fat pig, and must (take your pick): put on sackcloth and ashes and starve; give all your money to Hare Krishna; join their commune and give them all your money and live an ascetic life to achieve enlightenment; immediately have parts of your body cut off etc.
The warmists jump straight from an unproven, but probable, hypothesis to enforcing a range of courses of action with known dire, and many unknown, consequences, on the basis that we MUST DO SOMETHING BECAUSE THE SKY IS FALLING.
Their singular achievement to date, the Kyoto protocol, has actually increased emissions, including of the kind that were formerly controlled, by moving industrial output from well-regulated economies to India and China (where we are learning, quelle surprise, they are lying about even the highly elevated emissions they admit to).
Dame Thatcher, when talking about economics, pretty much summed up the general result of any of the left's ideas over the long run: they "traditionally do make a financial mess."

Actually, the wikipedia definition supports HLEBR's definition and gives a similar example to my analogy (scroll down to Strong v Weak precaution). I think you mix up which party bears the burden of proof that their actions are not harmful, given the scientific consensus on anthropogenic climate change.
I also disagree with your analogy. You pick extreme alternatives and present a false choice that caricatures sincere attempts to address climate change (do you really think a carbon tax is closer to physical mutilation than weight loss through exercise?). Furthermore, you argue semantics (incorrectly at best) when the ultimate message is risk management.
A market-based approach to reducing emissions is the most feasible approach to managing climate change. Geo-engineering so far is too expensive or uncertain. Carbon capture has yet to be shown as a feasible technology. If you can offer a better solution to reducing atmospheric carbon, the world would love to hear.
Until then, knee-jerk responses to cap-and-trade proposals with hysteria and overblown strawman arguments aren't very constructive (ex. tie-dyed Hare Krishnas, amputations, sky is falling). Also, cherry-picking arguments doesn't work either. Kyoto Protocol didn't increase emissions. Rather, nations ignored it, given one of the biggest carbon emitters in the world didn't sign. And that, my friend, is why you don't have to worry about tie-dyed hippies amputating you or cramming emissions controls down your throat. Reducing global carbon emissions requires global political will and cooperative effort to reduce a distant and widespread social cost- something not likely to happen as we've seen with Kyoto, Copenhagen, and all those other toothless meetings. So until you can offer constructive solutions better than market-based emissions controls (which will probably never happen), that's the best thing on the table.

Excellent Report.
Geoengineering the climate can focus on cooling the Arctic Ocean in order to slow the ice melt and increase albedo, reflecting incoming solar radiation back to space.
One potentially commercial method to achieve this goal is to float large sheets of reflective plastic just below the ocean surface, released from Norway into the Gulf Stream. The design would aim to optimise algae and fish growth, using wave energy to raise deep nutrient-rich water to the surface in 'Lovelock Tubes', and spreading this rich water across the surface sheet to mimic the upwelling of currents that are the source of the richest fisheries. This method would cool the surrounding water, reducing the heat input that is melting the sea ice. The systems would attract and feed fish with naturally produced algae, serving as efficient fish farms. They would float along the Gulf Stream (as shown at website divediscover The Arctic Ocean Circulation) into the Barents Sea, where produced fish could be harvested. Small initial prototypes would identify design issues for potential scale up. The natural geoengineering impact would be ecologically beneficial, cooling the Arctic Ocean to delay the risk of catastrophic warming.

There is also no serious doubt that carbon dioxide in the atmosphere traps heat, that there is more of it than there used to be, that the albedo effect is real, or that glaciers around the world are on average retreating.

Some of this is physics so basic that it's been understood for centuries, and is questioned only in relation to climate change. I can demonstrate the albedo effect using a black t-shirt and a white t-shirt in my back garden on a sunny day. Yes, even in England. :P

I assume that you mean those who do not believe in man-made climate change believe that as one believes in religion. The evidence is so strong that rejecting man-made climate change must be compared to a religious belief based on no evidence.

Stand on your head and you'll have it correct. Belief in man-made global warming without proof is the religion. For the left this isn't surprising. Praying at the alter of the mother earth diety is part of the initiation into being a member of socialist brotherhood. Control by the (leftist - we know what's good for you) government is key!

"There is no serious doubt about the basic cause of the warming." What a buffoon, the whole man-made climate change "theory" has made a complete mockery of the scientific method. We're not buying your leftist hogwash.

you obviously are not the brightest spark on the tree. the minute you use the term 'leftist hogwash' you immediately classify yourself at the 'buffoon' and know nothing of the science or the scientific method.

the science is over 180 years old, tens of thousands of scientific papers, what is happening was predicted by scientists before 1900, long before we had the recent crop of right wing know nothings.

Go do your homework. The scientific community NEVER predicted global cooling. That was stuff in the popular literature.

Go the skepticalscience web site. There are over 150 ways to try and deny global warming and climate change. they've debunked them all. Even give the science in introductory, intermediate, and advanced levels. They'll tellyou about global cooling,etc.

For me, the issue should center around heat transfer rather than temperature. The ice caps are moderating the temperature by melting. If we get to a point of substantially less ice the temperature will rise. The latent heat of water is substantial. We need to know how much faster the earth is absorbing and retaining energy. Then we need to know whether this will continue until the amount of ice no longer has a significant temperature maintenance effect.

FlyP says: "We need to know how much faster the earth is absorbing and retaining energy."

We already know that. The earth's energy balance is out of balance by 0.6W/m2. It's left as an exercise to FlyP to calculate the area of the earth in square meters and figure out how much excess energy is being deposited per day.

So, from my extensive research on a web site called Wikipedia, I learned that the earth has a surface area, land and water, of 510,072,000,000,000 m2. Multiply that by isleiij's 0.6W/m2 equals 310,000,000,000,000 Watts (1,000,000,000,000,000 Btu/hr.).

So assuming 0.6W/m2 is correct the earth is warming at a rate of 400,000 Hiroshima atomic bombs per day. Later I will research the estimated total amount of ice on earth and let you know how long until it is all melted, excluding the amount that is in isleiij's freezer.

It will be quite some time until it is all melted. Good luck with that. That is a far more difficult calculation, because of some of the physics of thick ice dynamics that is not well established.

The first to melt will be the ice sheet on Greenland and the West Antarctica Ice Sheet. Each of those will raise sea level by 7m or 21 ft. If, and when all the ice melts, sea level will rise by about 450 ft.

If you go to your maps, and look at the edge of the continental shelf, that is where sea level was 20,000 years ago during the last glaciation.

This article show some truth which is shocking for me. In fact, the earth warms continuously. However, we always can not prevent it effectively.That is the reason why we think "global warming" is earth's killer.

Yeah, the Earth has gone through severe climate change before. It's just that the humans haven't. Just because something may have occurred naturally in the past does not mean that A) it cannot be hastened, slowed, or eliminated by our modern technology and that B) our civilizations and institutions are capable of surviving its recurrence.

It is very unlikely that Watts adds anything to the understanding of any climate-related issue. After all, wasn't he the weatherman who said that the temperature record was wrong because the thermometers were mis-sited, and then had to eat that when BEST came out?

The WUWT posting is misleading. The basic argument is poorly formulated but seems to be that it is winds and ice drifting south that explain the disappearing of polar ice, and that therefore global warming is not the cause.

As so often with deniers, this argument combines elements that are true - changed wind patterns play a role - and then draws conclusions that are false. It does not follow that global warming is not a cause. Watts fails to ask the obvious question: what caused those wind patterns to change? Global warming could well change the winds, which then leads to melting. Melting ice costs energy, and that has to come from somewhere - from global warming. And Watts does not deny polar temperatures are rising - he even starts by pointing that out, but says it is "just one of many causes".

WUWT is designed to confuse. Watts takes money from the Heartland, but what his other sources of money are is unclear. Perhaps some more 'Anonymous Donors'? Blogs like WUWT try to create a reassuring parallel reality, and people go there to be confirmed in their beliefs that climate change is either not happening or that it is not due to human action and fossil fuel use. People who think the government, the UN and climate scientists are deceiving them but are blind to the deceit they flock to.

A polite suggestion to James Astill: James, please consider the hypothesis that the Global Warming story is a wrongheaded extrapolation of a brief uptick of temperatures between 1975 and 1998; that it is as illogical to extrapolate such a trend as it is to do so for a given period of the FTSE.

Climate has always changed. The big question is: Are recent changes exceptional and unprecedentd or are they within the range of historical variation? If it's the latter, the sooner that The Economist examines this the better. Your influential newspaper can help avoid the massive damage being caused to the economy by 'renewables'.

Of course climate has changed before. But has it ever changed when the Earth was supporting billions of people and an infrastructure (farms, cities, ports, dams, etc...) that was built around the existing climate?

Sure, if you don't like the charts, question the data.
But that "long-overdue" audit has already been done. By prof Mueller & colleagues in the BEST project (http://en.wikipedia.org/wiki/Berkeley_Earth_Surface_Temperature). With Koch money, no less.
They found that nothing was wrong with the data and that mainstream science is correct: the world is really warming. To suggest otherwise is, by now, utterly laughable.

It's time the Economist got out of the psuedo-science business and stick to its knitting. There is not one active climatologist who could support this article as written. This is a serious subject. "Skeptical" scientists and AGW "believers" all agree that some serious cycling is going on in the arctic, has been for millennia, and no quantitative answer has yet been proven about the effect of wind and the Arctic Oscillation compared to AGW. What is happening today, in the 1930's, and in Lief Erickson's time just cannot be explained in any major way by AGW.

It's all a giant conspiracy by those über-rich and über-powerful scientists and journalists, I tell you! Those greedy pigs are always out to exploit and abuse the poor, defenceless governments and MNCs.

I've read all their peer reviewed papers.
Can you identify one peer reviewed paper by a climate scientist that places AGW as the main driver in arctic ice?
That(rather than journalist's opinion)would be a major step forward in the debate since it would put some science into the claims and allow a real debate to progress.
Check out Geophysical Research Letters on the subject for the past 10 years and see if you can still agree with this article.